Historically, heavily loaded slow speed bearings, including, for example, the fifth wheel plate/trailer plate bearing connecting trucks and trailers have been lubricated with grease. In addition, due to the ready availability of chassis grease, where trucks and trailers are serviced, chassis grease has been and is used more frequently than any other grease.
Chassis grease or any standard grease or lubricant used to lubricate, for example, the fifth wheel plate/king pin plate bearing area does not have the mechanical or chemical characteristics that will provide lubrication in an efficient or environmentally safe manner. In order to produce an efficient and environmentally safe lubricant, particularly for fifth wheels, the basic problems and operation of this bearing area have to be addressed. The following areas are of concern.
(1) PROBLEMS OF LUBRICANT APPLICATION: Lubricating this bearing area has been and is generally accomplished by spreading grease on the fifth wheel plate. This is typically done by using an air or manual grease gun, by spreading grease obtained from a bucket or a barrel using a piece of corrugated paper or a wood board, or by squeezing grease directly out of a tube or a cartridge.
In any of the above application methods, the lubricant usually is not spread smoothly or evenly. It must be understood that grease application to this bearing area is not an enjoyable task. It is messy and therefore done as quickly as possible. Typically more grease is used than required or useful. This also leads to pollution problems. One attempt to make application easier is shown in Spiers Patent No. 4,913,263, issued Apr. 3, 1990, where lubricant is pre-packaged in plastic bags that are placed on the fifth wheel surface. The Spiers patent covers packaging, rather than lube composition.
Because the application and use of grease in this bearing area has been such a problem, there have been a number of patents which have attempted to overcome the problem by using plastic plates instead of grease. See, for example, Franks Patent No. 3,275,390 issued Sep. 27, 1966, Lowry Patent No. 3,704,924 issued Dec. 5, 1972, Szalay et al Patent No. 4,169,635 issued Oct. 2, 1979, Hunger Patent No. 4,457,531 issued Jul. 3, 1984, St. Louis Patent No. 4,542,912 issued Sep. 24, 1985 and Mamery Patent No. 4,805,926 issued Feb. 21, 1989. The Lowry and Szalay et al patents show the typical structure for the fifth wheel plate/king pin plate bearing area and the showings in these patents may be incorporated for reference in this application. Substituting plastic plates instead of grease increases the separation of the fifth wheel truck plate and the trailer king pin plate. This changes the nature of contact between the trailer king pin and its clamping mechanism located under the truck fifth wheel plate and may create operational safety problems.
(2) PROBLEMS OF LUBRICANT LOSS WHEN COUPLING TRACTOR AND TRAILER: The usual method of coupling is to back the tractor up to and then partially under the front of the trailer, so that the fifth wheel plate of the tractor is in correct alignment and contact with the king pin plate located on the trailer. If this is not done with care, much of the grease applied to the fifth wheel plate will be scraped off before coupling of the two vehicles. The scraped off grease is useless for lubrication and becomes a polluting material. This will be further commented on in more detail.
A similar problem occurs with plastic plates. If the coupling alignment is not correct, backing the tractor under the trailer can peel off or tear the plastic plate.
(3) OPERATING CONDITIONS IN SERVICE: The relative velocity of the fifth wheel plate on the truck relative to the king pin plate on the trailer is very low, typically much less than one foot per second. This bearing area also has very limited rotation. The relative movement between the two bearing areas is actually oscillation and never complete rotation. This relative movement only occurs when the tractor and trailer turn. On long portions of interstate highway, there is very little turning and therefore very little movement or oscillation of the two bearing surfaces relative to each other for hours at a time. There is more relative motion in the bearing area on winding roads and city streets. However, even in 90 degree city street corners, turns are typically made wide with the relative motion at less than 90 degrees so as to clear the corners.
The low relative motion in the present invention may be compared to open gear systems as described in Harris Patent No. 5,190,682 issued Mar. 2, 1993.
In the fifth wheel plate/king pin plate bearing lubricant of the present invention, it is desirable that there is enough flow and adhesion of lubricant to keep the bearing surface covered while under the loading conditions previously described. Without flow and adhesion, lubricant wipe-off in certain loaded zones typically becomes a problem and can result in galling and wear. In U.S. Pat. No. 2,094,576, finely divided insoluble solid filler, repeatedly stated as asbestos, is considered highly desirable to press a grease into sticks, or retain a grease in plug valves and eliminate cold flow.
The combination of polybutene and/or oils and/or thermoplastic polymer(s) and/or wax(es) in the adhesive lubricant creates a base material and/or end product substantially different in character, behavior and flow than the polybutene, oil and fibrous filler specified in U.S. Pat. No. 2,094,576.
With the typical very slow and limited oscillation, vertical loading from heavy cargo, vibration and irregular shock and harmonic loading, the rocking loads of cross winds, plus dirt, snow, salt, rain, rocks and trash constantly thrown up by the drive wheels as well as airflow around an unsealed bearing area, it is not surprising that typical chassis grease or any standard grease or lubricant including open gear lubricant will not last a long time and will pollute.
Water washout of the lubricant used in open bearings such as, for example, the fifth wheel/king pin plate bearing area is enhanced by the extremely heavy compression and shear loads. This is the result of mechanical working of the lubricant by the two bearing surfaces. This mechanical action aids and accelerates any tendency of the lubricant, especially portions of the lubricant exposed to water or moisture in this open bearing system, to emulsify. Emulsification typically lowers the viscosity of the lubricant and changes adhesion and load carrying characteristics of the lubricant and therefore contributes to premature lubricant breakdown in service. Mechanical working plus possible emulsification results in shorter lubricant service life, possible increased galling, scoring and/or wear of areas of the bearing surface. There is high washoff from these bearing areas with high resultant pollution from this bearing system.
(4) POLLUTION PROBLEMS WITH GREASE: As previously mentioned, grease is typically over-applied to this fifth wheel plate/king pin plate bearing area. A portion of this grease is typically scraped off and/or squeezed out during and immediately after the coupling of the truck with the trailer. Oscillation and continual loading constantly squeeze much of the remaining lubricant out of the bearing area. Also, the open bearing is constantly subject to water washout plus other operating conditions previously described. All of the above results in lubrication of the bearing area to be typically accomplished by 25 percent or less of the grease initially applied.
Loads, weather, drivers, equipment, roads and traffic are different each day and affect the amount of grease used. However, from inquiries and observations made over a number of years, it is estimated that from one half to one tube of grease or its equivalent is typically used once per week per truck on the fifth wheel bearing surface. Each tube is typically 14 or 14.5 oz. net weight.
The water washout, vibration, squeeze-out from constant load, together with other conditions previously described, typically remove almost all of the grease applied to this open system bearing from the previous week. The removal typically happens whether or not any of the grease actually was useful and used in lubrication of the bearing surface.
Vehicle sales and registration data do not indicate the precise number of trucks in operation with a fifth wheel. However, trade estimates are in the area of 1-1.5 million trucks with such a fifth wheel. Assuming the lower figure of one million trucks, since substantially all of the grease applied to the fifth wheel bearing area eventually becomes pollution, this means approximately 23-45 million pounds of grease pollution in the U.S. per year from just this one bearing area using existing lubricants.
It will be appreciated that a somewhat extended description of the fifth wheel plate/king pin bearing plate bearing system and its operation have been included. The reasons are that the lubrication products of this invention are intended to solve severe mechanical and environmental problems with slow speed, heavily loaded bearing surfaces. Fifth wheels provide a good example of the service conditions where these adhesive-lubricants are particularly suited for use. The mechanical, operational and pollution problems of the fifth wheel bearing area appear to be particularly severe, and, therefore, require extensive comment. Further, due to the unusually harsh operating conditions and characteristics of this bearing area, long periods of field testing have proven invaluable to obtain data as well as to test lubricants which provide superior performance under real world operating conditions. The preferred embodiments of the present invention are the result of this extensive field testing.